Ion implanters are conventionally utilized to place a specified quantity of dopants or impurities within semiconductor workpieces or wafers. In a typical ion implantation system, a dopant material is ionized, therein generating a beam of ions. The ion beam is directed at a surface of the semiconductor wafer to implant ions into the wafer, wherein the ions penetrate the surface of the wafer and form regions of desired conductivity therein. For example, ion implantation has particular use in the fabrication of transistors in semiconductor workpieces. A typical ion implanter comprises an ion source for generating the ion beam, a beamline assembly having a mass analysis apparatus for directing and/or filtering (e.g., mass resolving) ions within the beam, and a target chamber containing one or more wafers or workpieces to be treated.
Various types of ion implanters allow respectively varied dosages and energies of ions to be implanted, based on the desired characteristics to be achieved within the workpiece. For example, high-current ion implanters are typically used for high dose implants, and wherein medium-current to low-current ion implanters are utilized for lower dose applications. An energy of the ions can further vary, wherein the energy generally determines the depth to which the ions are implanted within the workpiece, e.g. to control junction depths in semiconductor devices.
As device geometries continue to shrink, shallow junction contact regions translate into requirements for higher ion beam currents at lower and lower energies. Additionally, requirements for precise dopant placement have resulted in ever-more demanding requirements for minimizing beam angle variation, both within the beam, and across the substrate surface. For example, in certain applications, high current implants at energies down to 300 electron Volts are desirable, while concurrently minimizing energy contamination, maintaining tight control of angle variation within the ion beam as well as across the workpiece, and also while providing high workpiece processing throughput.
At present, the preferred architecture to achieve high currents at low energies while minimizing angle variation is a dual-mechanical scan architecture, wherein the workpiece is mechanically scanned in two directions (e.g., a “fast” scan direction and a generally perpendicular “slow” scan direction) relative to a stationary spot ion beam. However, the relatively modest “fast” scan frequency utilizing this conventional architecture is limited by maximum accelerations that the mechanical systems can tolerate, and generally ranges between 1-3 Hz, thus limiting the maximum throughput of workpieces through the ion implanter. Ribbon beam systems, on the other hand, utilize ion beam optics for steering and shaping a ribbon-shaped ion beam, and are capable of achieving reasonably high currents at low energies. However, uniform current densities in conventional ribbon beam systems may be difficult to achieve, often at the expense of loss of angle accuracy. Hybrid scan technologies have also been provided utilizing electrostatic or magnetic “fast” scans of pencil or spot ion beams and mechanical “slow” scans of the workpiece, however, these conventional hybrid implanters further suffer beam transport problems resulting from the relatively higher space-charge density in a pencil beam and longer beam line length, especially at energies below 5 keV.
Conventionally, high dose implants and lower dose implants require the utilization of separate dose-specific ion implanters, wherein each implanter is designed for the respective higher or lower dose ion implantation architecture. Such a requirement for multiple ion implanters thus increases equipment cost to the semiconductor product manufacturer, as well as increasing the cost of ownership of the particular implanters. Thus, it can be appreciated that an improved beamline architecture is desirable for providing both a high dose implant and a lower dose implant utilizing a common ion implantation system.